Electron discharge device



G. J. AGULE ELECTRON DISCHARGE DEVICE May 3,' 1955 3 Sheets-Sheet 1Filed Sept. 19. 1950 ATTORNEYS X g I INVENTOR GEORGE [A6045 CM w I liiiiit a i E s n I a y 1955 G. J. AGULE 2,707,757

ELECTRON DISCHARGE DEVICE Filed Sept. 19. 1950 s Sheets-Sheet 2INVIENTOR 550/?65 J 66015 y 3, 1955 G. J. AGULE 2,707,757

ELECTRON DISCHARGE DEVEECE Filed Sept. 19, 1950 '3 Sheets-Sheet 3INVENTOR GA-ORGEJAQ/LE ATTO R N EYS United States Patent ELECTRONDISCHARGE DEVICE George J. Agule, Stamford, Conn., assignor to MachlettLaboratories Incorporated, Springdale, C0nn., a corporation ofConnecticut Application September 19, 1950, Serial No. 185,645

13 Claims. (Cl. 313-247) This invention relates to electron dischargetubes adapted for use at high frequencies. More particularly, theinvention relates to a novel electrode supporting structure and envelopeconstruction in a tube of the coaxial type.

Tubes adapted for high-frequency use require relatively close spacingbetween electrodes in orderv to obtain a sufiiciently short transit timefor the passage of electrons from cathode to anode. Also lead inductanceand capacitance must be reduced to a minimum. Furthermore it is highlydesirable that the structure and terminal arrangement be adapted for usewith coaxial tuning cavities as well as other tuning arrangements. Atthe same time, for high power applications the areas of the electrodesmust be large in order for the cathode to provide sutficient eiectronemission and for the anode to dissipate large amounts of heat.

The tube of the present invention is of the concentric cylindrical typehaving coaxially arranged terminals. By virtue of the concentriccylindrical arrangement the radial distance between electrode surfacesmay be made relatively small, and the length of the cylindrical surfacesprovides the necessary large areas for high-power use. In the specificembodiment described, a directlyheated filament cage is employedcomposed of a number of axially-extending filament wires in acylindrical configuration. Encircling the filament cage, and closelyadjacent thereto, is a grid cage likewise of cylindrical form andcoaxial with the filament cage. A coaxial cylindrical anode encirclesthe grid cage.

In tubes of this type a very important problemis the precise spacing andalignment of the cylindrically arranged electrodes.

Close spacing and accurate alignment is a common problem in the designand manufacture of high-frequency tubes. Most of the methods andtechniques developed up to the present time, however, are in the fieldof lowpower tubes. The development of tubular structures using coaxial,ring-seal construction has been possible because low-power tubes requireonly small light parts which may be drawn to intricate shapes with highuniformity, and which may be accurately handled by suitable jiggingtechniques. The use of planar electrodes is common in low-power tubes sothat the problem of spacing is more a matter of axial spacing than axialalignment. Even when cylindrical elements are employed, theinterelectrode spacing is not as small relative to the axiallength ofthe electrodes as it is in-large power tubes. Thus by the use of a fewaccurate die-drawn pieces to support the electrodes, and by providingsliding adjustments, it is possible at the present time to get extremelyclose electrode spacing in low-power tubes. Y

In high-power tubes the much larger size of the electrodes makes it farmore diificult to form the filament and grid electrode structures withthe necessary accuracy, and toobtain precise alignment with smallinterelectrode spacing. In order to obtain adequate ruggedness, theelectrodes must be strong and the electrode supports ice relativelymassive. Due to the required increased thickness of the metal parts, theintricate shapes possible in small tubes become very ditficult to formwith the necessary accuracy.

Heretofore the assembling of high-power tubes has been largely performedby skilled persons relying to a great extent upon visual accuracy.lthough some jigging equipment has been employed, the manner of mountingthe electrodes has been such as to still require the workers skilled eyefor accurate positioning.

In high-power tubes of the coaxial cylindrical type mentioned above,considerable difficulty is encountered in accurately forming thefilament cage so that it is absolutely symmetrical about its axis. Inaccordance with the present invention, a construction is provided whichenables the filament assembly to be produced with a high degree ofprecision. To this end, a so-called freehung self-supporting filamentcage is employed with mounting means at one end adapted to hold thefilament strands in precision alignment.

After the filament structure has been formed with the necessaryaccuracy, 21 further problem exists in assembling it with thesurrounding grid structure so as to maintain precise alignment and closespacing within the necessary close tolerances. The present inventionpro- I vides a structure which can be assembled readily with thenecessary precision by the aid of relatively simple jigging equipment.To this end, sturdy mounting means are provided for both filament andgrid assemblies and designed and constructed to enable them to be sealedtogether with great accuracy. Similar considerations are involved inassembling the anode structure with the grid and filament structure, andsimilar construction is provided.

Prior art tubes operating at high power, and hence at high voltages,have commonly been relatively fragile, because a large area of theirenvelopes were constructed of glass, or have been heavy and cumbersomedue to the use of heavy glass parts. The tube of the present inventionutilizes a metal concentric construction with ring seals made of aminimum amount of glass so as to yield a relatively light tube of greatmechanical strength, yet with adequate insulation to withstand highvoltages. The use of re-entrant sections has been avoided, since theglass in such sections is often difiicult to cool adequately.Furthermore, the tube is designed so that heat radiated from thefilament does not reach the glass seals, the tubular elements themselvesacting as heat shields.

Further features and advantages of the tube of the invention will inpart be pointed out hereinafter in connection with the description of aspecific embodiment thereof, and will in part be obvious to thoseskilled in the art.

The invention will be more fully understood by reference to thefollowing description of a specific embodiment thereof, taken inconjunction with the drawings in which:

Fig. 1 is a cross section taken along the axis of the tube, withportions of the filament and grid assemblies shown in elevation;

Fig. 2 is a cross section taken along the line 2-2 of Fig. 1 showing thearrangement of filaments and grid cage;

Fig. 3 is a cross section taken along the line 33 of Fig. 1 showing thefilament supporting rod structure;

Fig. 4 is a cross section taken along the line 4-4 of Fig. 1 showing theend mounting structure for the grid;

Fig. 5 is a cross section taken along the line 5-5 of Fig. 1;

Fig. 6 is a cross section taken along the line 6-6 of Fig. 1 showing thelower spacing plate of the grid cage; and

Fig. 7 is a cross section taken along the line 77 of Fig. 1 showing themanner of joining the filament wires at the free end of the filamentcage.

The tube illustrated in the drawings is capable of generating manykilowatts at frequencies extending up to the region of 150 megacycles.In order that a general idea of the size of the tube may be obtained, ina specific embodiment which has been operated with success the overallheight of the tube is approximately eighteen inches. It will, of course,be understood that the size of the tube and the proportions thereof maybe altered depending upon the use contemplated. In particular, byshortening the tube still higher frequency operation may be obtainedwhile still obtaining large power outputs.

In the drawings anode 10 is a deep cylindrical cup of highly conductivemetal such as copper. An exhaust tubulation 11 is sealed in the end wallof the cup and is sealed otf by a glass seal 12 after processing andevacuation. The seal-off 12 may be protected by a cap 13.

A water cooling system is employed in order to prevent overheating theanode in use. Water is fed into the tube at 14 in the space between neck19 and the exhaust tubulation, and passes upwards between anode 10 and acylindrical baflle 15. At the upper end of the anode the water passesaround the end of baffle 15 and down between the bafi le and the outercoaxial cylindrical anode support 16. Support 16 is soldered to theupper end of the anode at 17. An end cap 18 is soldered to the lower endof cylinder 16 and has an inwardly-extending flange 18 which is solderedto the neck 19. A number of holes 21 are provided in flange 18' topermit water to flow out of the jacket. The outer cylinder 16 may beformed in two pieces soldered together at joint 22, if desired forconvenience in assembly.

It will be observed that the annular flow of water in close contact withthe anode assures very eflicient cooling thereof.

A heavy annular metal disk 23 is soldered to the outside of cylinder 16and is provided with a metallic cylindrical section 24 soldered thereto.Cylinder 24 is advantageously of kovar so as to permit a strong seal tobe made between it and the vitreous ring seal 25.

A heavy grid support ring 26, with an olfset flange 26, has a shortmetal cylindrical section 27 soldered thereto. A cooperating metalcylindrical section 28 is sealed to the vitreous ring 25, and is henceadvantageously of kovar. Rings 27 and 28 are formed and sealed togetherat 30 in the manner described in my co-pending application Ser. No.118,878, filed September 30, 1949, now Patent No. 2,654,822. Asexplained in that application, the joining of members 27 and 28 formsthe final seal in the assembling of the tube. The cylindrical portionsof sections 24, 27 and 28 are advantageously of the same diameter tofacilitate accurate alignment during assembly.

It is advantageous to form vitreous ring 25 with a bowed out section asillustrated in order to provide strength. This will be discussed morefully hereinafter.

The grid cage is formed with a number of support rods 31 axially alignedand arranged in the form of a cylinder. At one end the grid support rodsare attached to grid mounting ring 32 (Fig. 4). At the other end theyare attached to a metal dish 33 (Fig. 6) which may be scalloped asillustrated. The grid wire 34 is helically wound around support rods 31.It will be readily appreciated that the grid cage as described can bereadily assembled as a unit with great precision. The grid mounting ring32 is mounted in position on the heavy grid support ring 26 by means ofthe metal collar 35 and bolts 36. Metal collar 35 has a triangular crosssection except for the recesses provided for bolts 36. It isadvantageously split as shown in Fig. 5 so as to permit ready assembly.It will be appreciated that the heavy ring 26 may be readily machinedwith great accuracy so as to precisely locate the grid cage in theassembled structure. Collar 35 also serves as a shield between the endportion of the grid and the adjacent anode.

The filament cage is formed of a number of wires 37, advantageously oftungsten, extending in an axial direction with cylindricalconfiguration. Advantageously an even number of wires are employed, andsixteen are used in the specific embodiment shown. The filament cage isof the so-called free-hung self-supporting type, being supported at oneend only in a manner to be described. The lower ends of the filamentwires 37 are bent inwards and then spaced around a central spool 38(Fig. 7). A fine wire 39 is then wound around the ends of the wires. Thewound portion may then be soldered or welded so as to form a joint ofgood conductivity between the ends of all the filament wires.

Filament wires 37 are attached to filament support rods 41 byradially-extending clips 42. These are advantageously formed of twopieces of metal (Fig. 5), riveted together, and cupped at the ends toreceive the filament wires and support rods. The use of clips 42 permitthe rods 41 to have a sufficiently srn-all radius of configuration 'topass through ring 26 during assembly while permitting a larger radius ofconfiguration for the filament wires 37 for close spacing with the grid.The clips permit attaching the filament wire cage to the rods after thefilament supporting structure has been assembled, thus avoidingpossibility of damage to the relatively fragile wire cage. If desired,however, other means for attaching the filament wires to the supportingstructure may be employed.

A pair of heavy coaxial cylinders 43, 44 are provided for supporting thefilament structure. Alternate support rods 41 are attached to aninwardly-extending flange on cylinder 43. The intermediate support rods41 extend through holes 45 provided in the flange (see Fig. 3) and areattached to cylinder 44. Instead of employing holes 45, the flange ofcylinder 43 may be scalloped to allow alternate rods 41 to pass therebyin non-contacting relationship. Respective rods 41 are inserted intocorresponding holes in cylinders 43 and 44, and the holes are drilled inrespective circular patterns having the same radius. Cylinder 44 isclosed by an end cap 46, soldered thereto. A short metallic cylindricalsection 47 is soldered to end cap 46, and a section 48 of the samediameter is soldered to ring 49 which in turn is soldered to cylinder43. Sections 47 and 48 are joined together by ring seal 51 of vitreousmaterial.

This design of the filament structure enables the filament wires to beassembled and maintained in alignment with great precision. Cylinders 43and 44 may be held in a fixture in a glass lathe in accurate alignmentwhile vitreous ring seal 51 is formed. This insures the correctalignment of filament support rods 41 inasmuch as the correspondingholes in cylinder 44 and the flange of cylinder 43 were initiallydrilled in circular patterns of the same radius. This assures, in turn,that filaments 37, affixed to support rods 41 by clips 42 will beprecisely aligned axially, and that the cylindrical configuration of thefilament wires will be in precise axial alignment with the terminalcylinders 43, 44.

Annular ring 49 is provided with a short metal cylindrical section 52and heavy ring 26 is provided with a cooperating section 53 of likediameter. Sections 52 and 53 are then joined together by ring seal 54 ofviterous material. Here again, it is readily apparent that by holdingthe cathode assembly and the heavy ring 26 in a fixture during theformation of ring seal 54, the ring 26 may be precisely aligned with thefilament terminal cylinders 43, 44 and the remainder of the filamentstructure. Then, when the grid cage is afl'rxed to heavy ring 26, aspreviously described, the grid and filament structures are mounted andmaintained in correct alignment with great precision.

The anode structure previously described, including ring 23, vitreousring 25 and the short metal ring 28 may likewise be assembled in a glasslathe wit-h precision so that ring 28 is correctly aligned with theanode. When both assemblies have been completed, they may be joinedtogether at 30 as previously described.

any advantageous features of the tube of the present invention will nowbe apparent. Since the filament terminal and support cylinders 43, 44are solid and heavy, holes may be precision bored therein at the sameradius and parallel to the axis thereof to assure perfect parallelism ofthe heavy filament support rods 41. Cylinders 43 and 44 may be readilyheld in alignment during the formation of ring seal 51, and shortcylinders 47, 48 may be advanced toward each other a precise amount in aglass lathe during the formation of the ring seal so that the resultingterminal structure is correctly aligned and accurately spaced in theaxial direction. When the filament wires 37 are attached to support rods41 by means of clips 42,- the resulting filament structure is extremelyrugged and of proper dimensions and symmetry.

The grid support ring 26 is likewise heavy and massive so that it may bemachined with great accuracy and tapped bores precisely located thereinfor receiving bolts 36. Ring 26 may be accurately aligned and axiallyspaced with respect to the filament structure during the formation ofglass seal 54 in the same manner as just explained for the two filamentterminals. The grid cage may be separately assembled with precision andthen secured to terminal ring 26.

Similarly the anode structure may be assembled with precision and thenjoined to the grid ring 26 in the manner above described so as to secureand maintain accurate alignment.

While glass seals are employed, the amount of glass used is kept to aminimum and this factor, together with the use of heavy metal supportsfor the electrodes insures a rugged tube.

The bowing of the largest glass section further assures adequateruggedness. It will be understood that when the tube is evacuated theatmospheric pressure tends to press the ends of the tube toward eachother in an axial direction, thus placing all the glass seals 25, 51 and54 under compression. This is advantageous in that glass is muchstronger under compression than under tension. At the glass seal 25,there is also a radially inwards pressure produced by the atmosphere,and the bowing provides strength against this pressure.

The tube also has highly desirable electrical characteristics. Theprecision of the mechanical assembly permits employing closely spacedcylindrical configurations to reduce transit time and insures uniformityof characteristics from tube to tube. The support members for eachelectrode are separated from those of each other electrode so as toreduce capacitance therebetween. Lead inductance is minimized by theconcentric configuration and the straight paths involved. Theelimination of all intricate parts not only simplifies the constructionof the tube but greatly reduces the grid-'to-filament capacitance. Theuse of heavy filament terminal cylinders assures a low resistance pathto the filament wires, and the heavy grid ring 26 provides a low-losspath to the grid cage.

It will be understood that many of the details of construction may bechanged within the spirit and scope of the invention and that some ofthe features thereof may be employed in a given case while omittingothers.

I claim:

1. An electron discharge tube which comprises a pair ment with the othersupport, a filament cage structure having axially-extendingcylindrically-arranged filament wires with respective axially-extendingcylindrically-ararranged mounting sections, a plurality of alternate 6mounting sections being attached to the mounting poitions of said flangein a circular configuration of selected diameter and the intermediatemounting sections passing through the open portions of said flange andbeing attached to said other support in a concentric circularconfiguration of the same diameter, a pair of coaxial metal cylindricalsections of like diameter joined to respective cylindrical supports andsealed together by an insulating ring seal, said sections and sealextending between the outer support and the outer end of the innersupport to form a non-reentrant seal, a coaxial heavy annular metal gridsupporting ring extending generally laterally of the tube and positionedaxially between said filament supports and said filament wires, one sideof said ring being insulatedly joined to the outer filament support by'apair of coaxial metal cylindrical sections and an interposed insulatingring seal, the inner diameter of said supporting ring being less thanthat of the last-mentioned ring seal and less than that of thecylindricallyarranged filament wires, the other side of said supportingring having an accurately formed annular surface, a cylindrical gridstructure having a mounting ring at one end thereof, said mounting ringbeing secured to said annular surface to position said grid structure incoaxial encircling relationship with said filament wires, and a coaxialcylindrical anode encircling said grid.

2. An electron discharge tube which comprises a pair of concentriccylindrical metal filament supports, the inner of said supportsextending axially beyond the outer support, a flange on one of saidsupports having alternate mounting portions and open portions in axialalignment with the other support, a filament cage structure havingaxially-extending cylindrically-arranged filament wires with respectiveaxially-extending cylindricallyarranged mounting sections, a pluralityof alternate mounting sections being attached tovthe mounting portionsof said flange in a circular configuration of selected diameter and theintermediate mounting sections passing through the open portions of saidflange and being attached to said other support in a concentric circularconfiguration of the same diameter, a pair of coaxial metal cylindricalsections of like diameter joined to respective cylindrical supports andsealed together by an insulating ring seal, said sections and sealextending be tween the outer support and the outer end of the innersupport to form a nou-reentrant'seal, a coaxial heavy annular metal gridsupporting ring extending generally laterally of the tube and positionedaxially between said filament supports and said filament wires, a pairof coaxial metal cylindrical sections of like diameter joined to oneside of said ring and to said outer filament support respectively andsealed together by an insulating ring seal, the inner diameter of saidsupporting ring being less than that of the last-mentioned ring seal andless than thatof the cylindrically-arranged filament Wires, acylindrical grid structure secured to the other side of said supportingring in coaxial encircling relationship with said filament wires, and acoaxial cylindrical anode encircling said grid.

3. An electron discharge tube which comprises a pair of concentriccylindrical metal filament supports, the inner of said supportsextending axially beyond the outer support, a flange on one of saidsupports having alternate mounting portions and open portions in axialalignment with the other support, a filament cage structure havingaxially-extending cylindrically-arranged filament wires with respectiveaxially-extending inwardly-offset cylindrically-arranged mountingsections, a plurality of alternate mounting sections being attached tothe mounting portions of said flange in a circular configuration ofselected diameter and the intermediate mounting sections passing throughthe open portions of said flange and being attached to said othersupport in a concentric circular configuration of the same diameter, apair of coaxial metal cylindrical sections of like diameter respectivelyjoined at one end thereof to respective cylindrical supports, theopposite ends of said cylindrical sections being sealed together by avitreous ring seal, said sections and seal extending between the outersupport and the outer end of the inner support to form a non-rccntrantseal, a coaxial heavy annular metal grid supporting ring extendinggenerally laterally of the tube and positioned axially between saidfilament supports and said filament wires, a pair of coaxial metalcylindrical sections of like diameter respectively joined at one endthereof to one side of said ring and to said outer filament support, theopposite ends of the last-mentioned cylindrical sections being sealedtogether by a vitreous ring seal, the inner diameter of said supportingring being greater than said cylindrically-arranged mounting sectionsbut less than that of the last-mentioned ring seal and less than that ofthe cylindrically-arranged filament wires, a cylindrical grid structurehaving a mounting ring at one end thereof, said mounting ring beingsecured to the other side of said grid supporting ring to position saidgrid structure in coaxial encircling relationship with said filamentwires, and a coaxial cylindrical anode encircling said grid.

4. An electron discharge tube which comprises a pair of concentriccylindrical metal filament supports, the inner of said supportsextending axially beyond the outer support, a flange on one of saidsupports having alternate mounting portions and open portions in axialalignment with the other support, a filament cage structure havingaxially-extending cylindrically-arranged filament wires with respectiveaxially-extending eylindrically-arranged mounting sections, a pluralityof alternate mounting sections being attached to the mounting portionsof said flange in a circular configuration of selected diameter and theintermediate mounting sections passing through the open portions of saidflange and being attached to said other support in a concentric circularconfiguration of the same diameter, a pair of coaxial metal cylindricalsections of like diameter joined to respective cylindrical supports andsealed together by an insulating ring seal, said sections and sealextending between the outer support and the outer end of the innersupport to form a non-reentrant seal, a coaxial heavy annular metal gridsupporting ring extending generally laterally of the tube and positionedaxially between said filament supports and said filament wires, a pairof coaxial metal cylindrical sections of like diameter joined to oneside of said ring and to said outer filament support respectively andsealed together by an insulating ring seal, the inner diameter of saidsupporting ring being less than that of the last-mentioned ring seal andless than that of the cylindricallyarranged filament wires, acylindrical grid structure secured to the other side of said supportingring in coaxial encircling relationship with said filament wires, acoaxial cylindrical anode encircling said grid, and a pair of coaxialmetal cylindrical sections of like diameter joined to said gridsupporting ring and to said anode respectively and sealed together by aninsulating ring seal, the metal section joined to said supporting ringextending axially beyond the adjacent end of the anode whereby therespective ring seal is shielded from the filament Wires.

5. An electron discharge tube which comprises a pair of concentriccylindrical metal filament supports, the inner of said supportsextending axially beyond the outer support, a flange on one of saidsupports having alternate mounting portions and open portions in axialalignment with the other support, a filament cage structure havingaxially-extending cylindrically-arranged filament Wires with respectiveaxially-extending cylindrically-arranged mounting sections, a pluralityof alternate mounting sections being attached to the mounting portionsof said flange in a circular configuration of selected diameter and theintermediate mounting sections passing through the open portions of saidflange and being attached to said other support in a concentric circularconfiguration of the same diameter, a pair of coaxial metal cylindricalsections of like diameter respectively joined at one end thereof torespective cylindrical supports, the opposite ends of said cylindricalsections being sealed together by a vitreous ring seal, said sectionsand seal extending between the outer support and the outer end of theinner support to form a non-reentrant seal, a coaxial heavy annularmetal grid supporting ring extending generally laterally of the tube andpositioned axially between said filament supports and said filamentwires, a pair of coaxial metal cylindrical sections of like diameterrespectively joined at one end thereof to one side of said ring and tosaid outer filament support, the opposite ends of the second-mentionedcylindrical sections being sealed together by a vitreous ring seal, theinner diameter of said supporting ring being less than that of thelast-mentioned ring seal and less than that of thecylindrically-arranged filament wires,- a cylindrical grid structuresecured to the other side of said supporting ring in coaxial encirclingrelationship with said filament wires, a coaxial cylindrical anodeencircling said grid, and a pair of coaxial metal cylindrical sectionsof like diameter respectively joined at one end thereof to said gridsupporting ring and to said anode, the opposite ends of thelast-mentioned cylindrical sections being sealed together by a vitreousring seal and the metal section joined to said supporting ring extendingaxially beyond the adjacent end of the anode whereby the respective ringseal is shielded from the filament wires.

6. A high-power electron discharge tube for high-frequency use whichcomprises a pair of concentric cylindrical metal filament supports, theinner of said supports extending axially beyond the outer support, aflange on one of said supports having alternate mounting portions andopen portions in axial alignment with the other support, a plurality ofaxially-extending mounting rods attached to the mounting portions ofsaid flange in a cylindrical configuration of selected diameter, a likeplurality of axially-extending mounting rods passing through the openportions of said flange and attached to said other support in acylindrical configuration of said selected diameter, a free-hungself-supporting filament cage having axially-extending wires arranged ina cylindrical configuration of larger diameter than said mounting rodsand connected together at the free end thereof, alternate wires beingconnected to the first mentioned mounting rods and intermediate wiresbeing connected to the second-mentioned mounting rods, a pair of coaxialmetal cylindrical sections of like diameter respectively joined at oneend thereof to respective cylindrical supports, the opposite ends ofsaid cylindrical sections being sealed together by a vitreous ring seal,said sections and seal extending between the outer support and the outerend of the inner support to form a non-reentrant seal, a coaxial heavyannular metal grid supporting ring extending generally laterally of thetube and positioned axially between said filament supports and saidfilament wires, a pair of coaxial metal cylindrical sections of likediameter respectively joined at one end thereof to one side of said ringand to said outer filament support, the opposite ends of thesecond-mentioned cylindrical sections being sealed together by avitreous ring seal to form a non-reentrant seal, the inner diameter ofsaid supporting ring being greater than said cylindrically-arrangedmounting rods but less than that of the last-mentioned ring seal andless than that of the cylindrically-arranged filament wires, acylindrical grid structure having a mounting ring at one end thereof,

said mounting ring being secured to the other side of said gridsupporting ring to position said grid structure in coaxial encirclingrelationship with said filament Wires, a coaxial cylindrical anodeencircling said grid, and a pair of coaxial metal cylindrical sectionsof like diameter respectively joined at one end thereof to said gridsupporting ring and to said anode, the opposite ends of thelast-mentioned cylindrical sections being sealed together by a vitreousring seal and the metal section joined to said supporting ring extendingaxially beyond the adjacent end of the anode whereby the respective ringseal is shielded from the filament wires.

7. A high-power electron discharge tube for highfrequency use whichcomprises a first metal cylinder having a plurality of axially-extendingcylindrically-arranged mounting rods mounted in equally-spaced holes inone end thereof, a second coaxial metal cylinder encircling said firstcylinder and having a flange overlapping said one end and provided withholes through which said rods pass in non-contacting relationship, theother end of said first cylinder extending axially beyond said secondcylinder, a like plurality of axially-extending mounting rods mounted inequally-spaced holes in said flange in a cylindrical configuration ofthe same diameter as the first-mentioned rods and alternating therewith,a freehung self-supporting filament cage having axially-extendingcylindrically-arranged wires connected together at the free end thereof,the cylindrical diameter of said wires being larger than that of saidmounting rods, alternate wires being connected to the first-mentionedmounting rods and intermediate wires being connected to thesecond-mentioned mounting rods, a pair of coaxial metal cylindricalsections of like diameter respectively joined at one end thereof torespective metal cylinders, the opposite ends of said cylindricalsections being sealed together by a vitreous ring seal, said sectionsand seal extending between the second cylinder and the outer end of thefirst cylinder to form a non-reentrant seal, a coaxial heavy annularmetal grid supporting ring extending generally laterally of the tube andpositioned axially between said filament supports and said filamentwires, a pair of coaxial metal cylindrical sections of like diameterrespectively joined at one end thereof to one side of said ring and tosaid second cylinder, the opposite ends of the second-mentionedcylindrical sections being sealed together by a vitreous ring seal toform a non-reentrant seal, the inner diameter of said supporting ringbeing greater than said cylindrically-arranged mounting rods but lessthan that of the last-mentioned ring seal and less than that of thecylindrically-arranged filament wires, a cylindrical grid structurehaving a mounting ring at one end thereof, said mounting ring beingsecured to the other side of said grid supporting ring to position saidgrid structure in coaxial encircling relationship with said filamentwires, a coaxial cylindrical anode encircling said grid, and a pair ofcoaxial metal cylindrical sections of like diameter respectively joinedat one end thereof to said grid supporting ring and to said anode, theopposite ends of the last-mentioned cylindrical sections being sealedtogether by a vitreous ring seal of outwardly-bowed axial cross sectionand the metal section joined to said supporting ring extending axiallybeyond the adjacent end of the anode whereby the respective ring seal isshielded from the filament wires.

8. An electron discharge tube which comprises an envelope, a pair ofconcentric cylindrical metal filament supports arranged one within theother to extend into the envelope, the inner of said supports extendingaxially beyond the outer support at the end terminated at the envelope,a flange on the inner end of one of said supports having alternatemounting portions and open portions in axial alignment with the othersupport, a filament cage structure having axially-extendingcylindrically-arranged filament wires with respective axially extendingfilament mounting sections, a plurality of cylindrically-arrangedalternate filament mounting sections being attached to the mountingportions of said flange in a circular configuration of selected diameterand intermediate filament mounting sections passing through the openportions of said flange and being attached to said other support in aconcentric circular configuration of the same diameter, a pair ofcoaxial circular heavy metallic envelope portions at which therespective filament supports terminate, a pair of coaxial metal sectionsof right circular cylindrical shape and of like diameter joined to therespective heavy envelope portions, an insulating ring seal joining saidpair of metal sections, said metal sections and ring seal, in order toform a non-reentrant seal, providing a direct connection in the form ofa cylindrical column extending between and terminating respectively atthe heavy envelope portion which terminates the outer filament supportand the heavy metallic envelope portion which is affixed to the innerfilament support, a coaxial cylindrical grid encircling said filamentwires and a coaxial cylindrical anode encircling said grid.

9. An electron discharge tube which comprises an envelope, a pair ofconcentric cylindrical metal filament supports arranged one within theother to extend into the envelope, the inner of said supports extendingaxially beyond the outer support at the end terminated at the envelope,a flange on the inner end of one of said supports having alternatemounting portions and open portions in axial alignment with the othersupport, a filament cage structure having axially-extendingcylindrically arranged filament wires with respective axially-extendingcylindrically-arranged filament mounting sections, a plurality ofalternate filament mounting sections being attached to the mountingportions of said flange in a circular configuration of selected diameterand intermediate filament mounting sections passing through the openportions of said flange and being attached to said other support in aconcentric circular configuration of the same diameter, a pair ofcoaxial circular heavy metallic envelope portions at which therespective filament supports terminate, a pair of coaxial metalcylindrical sections of right circular cylindrical shape and of likediameter respectively joined at one end thereof to the respective heavyenvelope portions, an insulating ring seal joining said pair of metalsections, said metal sections and ring seal, in order to form anon-reentrant seal providing a direct connection in the form of acylindrical column extending between and terminating respectively at theheavy envelope portion which terminates at the outer filament supportand an outward extending part of the heavy envelope portion which isaffixed to the inner filament support, a coaxial cylindrical gridencircling said filament wires, and a coaxial cylindrical anodeencircling said grid.

10, A coaxial electron tube having an envelope providing support forelements within the tube envelope, said envelope comprising at leastthree heavy highly-conductive terminal members of circular shapecoaxially arranged to avoid reentrant sections, each of which terminalshas an aperture at its center, except the terminal which forms an endcap, right circular cylindrical columns directly joining adjacent pairsof terminal members, at which members the columns terminate, each ofwhich columns consists of a pair of relatively light gauge coaxial metalcylindrical sections of like diameter joined by an insulating ring seal,and support members for rigidly supporting electrodes on each of theterminal members whereby close spaced electrodes are prevented fromshorting from one to the other.

11. A coaxial electron tube having an envelope providing support forelements, including the filament, within the tube envelope, saidenvelope comprising at least three heavy highly-conductive terminalmembers of circular shape coaxially arranged to avoid reentrantsections, each of which terminals is a metallic ring, except theterminal which forms an end cap, right circular cylindrical columnsdirectly joining adjacent pairs of terminal members, at which membersthe columns terminate, each of which columns consists of a pair ofrelatively light gauge coaxial metal cylindrical sections of likediameter joined by an insulating ring seal, heavy coaxial cylindricalsupport members extending into the envelope from each of said terminalmembers, and electrodes rigidly supported on each of the terminalmembers whereby said electrodes may be close spaced without danger ofshorting from one to the other.

12. A coaxial electron tube having an envelope providing support for thegrid and two sides of the filament, respectively, within the tubeenvelope, said envelope comprising three heavy highly-conductiveterminal members of circular shape coaxially arranged to avoid reentrantsections, at least two of which terminals are metallic rings, rightcircular cylindrical columns directly joining adjacent pairs of terminalmembers, at which members the columns terminate, each of which columnsconsists of a pair of relatively light gauge coaxial metal cylindricalsections of like diameter joined by an insulating ring seal, heavycoaxial cylindrical support members extending into the envelope fromeach of said terminal members, and electrodes rigidly mounted on thesupport members in such a manner that they may be close spaced to oneanother without shorting from one to the other.

13. A coaxial electron tube having an envelope providing a filamentsupport structure within the tube envelope, said envelope comprising apair of heavy highlyconductive terminal members of circular shape and ofdifferent size coaxially arranged to avoid reentrant sections, thelarger of which terminals is a metallic ring, a right circularcylindrical column directly joining said terminal members, at whichmembers the column terminates, which column consists of a pair ofrelatively light gauge coaxial metal cylindrical. sections of likediameter joined by an insulating ring seal, heavy coaxial cylindricalsupport members extending into the envelope from each of said terminalmembers, and a filament structure rigidly supported upon the heavycoaxial support members in such a manner that alternate strands of thefilament extend to one support member and intermediate strands extend tothe other support member.

References Cited in the file of this patent UNITED STATES PATENTS2,489,872 Elder et al. Nov. 29, 1949 2,489,873 Thorson Nov. 29, 19492,542,639 De Walt Feb. 20, 1951

